feat(CI/Travis): use Ubuntu 18.04 + update min clang version (#2232)

.travis.yml

@@ -1,6 +1,5 @@
 sudo: required
-dist: xenial # (16.04)
-# bionic (18.04) is not yet available in travis
+dist: bionic # (18.04)
 
 language: cpp
 

apps/ci/ci-before_install.sh

@@ -4,8 +4,8 @@ set -e
 
 if [ "$TRAVIS_BUILD_ID" = "1" ]
 then
-  export CCOMPILERC="clang-3.8"
-  export CCOMPILERCXX="clang++-3.8"
+  export CCOMPILERC="clang-6.0"
+  export CCOMPILERCXX="clang++-6.0"
 
   echo "set root password"
   export DB_RND_NAME=$(cat /dev/urandom | tr -dc 'a-z' | fold -w 5 | head -n 1)
@@ -18,9 +18,4 @@ elif [ "$TRAVIS_BUILD_ID" = "2" ]
 then
   export CCOMPILERC="clang-7"
   export CCOMPILERCXX="clang++-7"
-
-  echo "add custom APT repository llvm-toolchain-xenial-7"
-  wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
-  echo "deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-7 main" | sudo tee -a /etc/apt/sources.list
-  sudo apt-get update -qq
 fi

apps/ci/ci-install.sh

@@ -7,8 +7,8 @@ bash ./acore.sh "install-deps"
 
 if [ "$TRAVIS_BUILD_ID" = "1" ]
 then
-  echo "install clang-3.8"
-  sudo apt-get install clang-3.8
+  echo "install clang-6.0"
+  sudo apt-get install clang-6.0
 elif [ "$TRAVIS_BUILD_ID" = "2" ]
 then
   echo "install clang-7"

src/common/Cryptography/OpenSSLCrypto.cpp

@@ -22,6 +22,7 @@ static void lockingCallback(int mode, int type, const char* /*file*/, int /*line
 
 static void threadIdCallback(CRYPTO_THREADID * id)
 {
+    (void)id;
 /// ACE_thread_t turns out to be a struct under Mac OS.
 #ifndef __APPLE__
     CRYPTO_THREADID_set_numeric(id, ACE_Thread::self());
@@ -37,7 +38,10 @@ void OpenSSLCrypto::threadsSetup()
     {
         cryptoLocks[i] = new ACE_Thread_Mutex();
     }
+    (void)&threadIdCallback;
     CRYPTO_THREADID_set_callback(threadIdCallback);
+
+    (void)&lockingCallback;
     CRYPTO_set_locking_callback(lockingCallback);
 }